Method of and means for indicating direction



ATTORNEY n w m B n m 0 mm WW mw 1R 3 n 5 2 A w u a B 3 Q u s l v ma g flflfi mm 3 K.- -Ei @M w R T Aug. 25, 1931.

A. w. BROWN METHOD OF AND MEANS FOR INDICATING DI RECTION Filed Aug. 14, 1950 Patented Aug. 25, 1931 unrrsn srArEs- ARTHUR WHITTEN BROWN, 01? LANGLAND, SWANSEA, WALES METHOD or AND MEANS FOR mm'onzrme' DIRECTION" Application filed August 14,1930, Serial No 475,339, and in :Great trim a ust 13, 1929.

This invention relates .to wireless or radio direction finding systems and has for its main object to provide a system in which an instrument provides a continuous and posi- 5 tive indication or a record of-the hearing or direction of a high frequency wave front irrespective of any movement of the axis of reference.

According to the invention a receiving aerial or search coil of the directional type is rotated at a fixed speed ofsay 'revolu tions per second and the high frequency eurrents received by. said rotating aerial or search (3011 are rectified, with amplification tween the rectif ed current and a reference current of the same frequency is measured by an instrument such as a synchroseope'," ,powerfactor meter, v oscillograph,- oscil-lo--' or the like which thus provides a posi-' tive indication of the bearing of the wave front. Such instrument may have such a scale or chart and/or be so calibrated'that its point or the equivalent gives a compass 5 bearing indication of the position of the transmitting stationor even points directly towards the latter and the indication will be properly given irrespective of the position or direction of travel of the ship or aircraft 0 which carries the direction finding system.

Obviously the instrument mayalternatively or in addition provide a permanent record of the bearings of wave fronts.

In carrying out the invention the rotating portion may be of the tuned or tunable frame aerial type and the currents may be collected therefrom by slip rings or by a condenser, being received directly, or by a fixed aerial and field coil syste'msuch as of 40 the type used in Bellini-Tosi radiogonimeters. The aerial may be constructed so I that the strength of the current which is received compared with the direction of the transmitting station approximatesin form to a sine-curve.

if necessary, and 'the phase ditfercnceibe The rotatinggportionmay be mounted on a vertical shaft whichis rotated by electric, hand or wind'power or in any other convenient way, and the rotor, such as the field magnets, of analternating current generator may be secured to or connected by gearing with said shaftv so as to rotate proportionally therewith, whilst the stator of the generator is fixed but preferably adjustable in the direction of rotation. The generator need only be a small machine capable of'delivery say 20 watts at cycles, and the field magnets may thus be of the permanent type.

v able,.this'byq'suitable transforming, may be used aslthe reference current, and the aerial may. be rotated by a synchronous motor "driven.- from the supply.

- ;.'The received high frequency currents may be amplified at high frequency and then rectified so as to obtain a low frequency alternating current of say 50cycles which may b'eamplified and corrected as to wave form so as to obtain a current substantially equal' in amplitude to the reference current, for

properly operating the instrument.

The invention also comprises an arrangement of two or more systems as above set forth for obtaining positions by cross bearings. Thus the receiving systems may be vspaced apart and arranged to rece ve the same or different transmission simultaneously whilst the indicating instruments are adjacent one to another, being arranged for instance on a map or chart, the position being found from the intersection of the ceivers may be close together and tuned-to receive different transmissions simultaneously.

Bolyphase aerials, generators and instruments may in some cases be used with advantage.

'To enable the invention to be clearly pointers, or alternatively the several repanying drawings, inwhich I 1 I i v Figure l a diagrammatic representation 1 pa' fl a;,3510f cliimetionfinding;system inaccordance:

, died :arran 'engient for; '0llc:t-in -the aerial.

a r, P)

with the invention. g

1 'lfigui'e Bis a perspective xicwof 21'lI1I1(ili= currents.

lligure 3 is a' sccticmtal plan viewof a further arrangement in!" gwllecting: the: ac

, rial currents. y 7 ;-;-;-;'Figuret1sadiagram.illustratingamaths d of correcting the: received currents as to wvaveform,and, a

to Figure 1 of the draw:- I i rigs, 1; represents a frame aerial fixed upon g g gp; qqgqa xcrtical shaft 2; and: having its; rends,

brought out to slip "rings 1 S, I engaged by collector; brushes 4, i The: shaft: 2 is: rotated I I by any convenient; means connected,- for ini stance, to a shaft :xvlnch drives, the shaft;

i; :2 r g g aring 6,: The; shafts may be:

by means of an electr c mos itself; rotted:

ir, an an ,1 scrcwor from any existing-rot ng; dev ce such as the engine :shaftofa ship i l Qor by a synchronous; motor: fori example; i 3-; The collector brushes 4; are connected by illustrated variable; condenser 8 g for z the i frame aerial; -2.:-;The leads: '8 are also con-:

necteel ie the high frequency amplifier 9,: the output of which is connected toa rectifier 10, and'the output of the latter is connected to a low frequency amplifier 11, the output of which is, in turn, connected to one clementof an instrument 12 capable of indicating phase difference. Said instrument may comprise a synchroscope, powerfactor meter, or oscillograph, oscilloscope or the like. The instrument '12 may be connected to the amplifier 11 if desired through a transformer indicated by the dotted rectangle Reference numerals 14 and 15 represent respectively the high tension and low tension busbars of the amplifiers and rectifier 9, 10 and 11. A galvanoineter 10 may be employed for checking the tuning adjustment.

In the arrangement shown in Figure 1, the shaft 2 carries the rotor of .a small alternating current generator 16, having such a number of poles that the alternating current derived from the slip rings 17 of the gen erator has a frequency equal to that derived from the frame aerial 1. The stator of the generator 16 is preferably angularly adjustable in azimuth about the shaft 2, and for this purpose the hand-wheel 18 and gearing 19 may be provided, together with a suitable brake (not shown) if necessary. The current generated by the machine 16 is passed,

rating a method g positionsor directions by cross i rangement, therein leads: 1 with: tuning mea'ns such as the I Instead: of slip rings 3' condenser plates 20 and21 may 'beIemp-loyedfor-(reflecting 7 Thus, i

assiwwn in Figure 2, the leads? may be connectedto fixed plates2 0 whilst the teri nrinalsof the frameaerialmaybeconnected to rotating P ates 21 fixed to the shaft 2.

the currents received by theaerial 1.

rReferringzto Fi gurefi,thefurtherar illustrated; comprises I field coiis 22 for connection to Bellini-Tosi loops or adcoc k; aerials, having respective of the aerial are spaced outwith the object i i of cerium currents L which approximate in form'to:sine wavepa I;

: In Figure 4 is illustrated by way: of exam 7 i ple' means for correcting the rectified curronts as to wave form, said mea'ns campus- 5 l ingtherectifier valvefifi, coupled to a lowi' -v frequency amplifying valve "27 by meansofa: resistance 28, condenser 29, and: grid leak I I I i 3.0,; the values of which elements are chosen 1 i I i l so as-to provide the requisite time constant in relation to frequency due to the speed n 3 I of rotation of the aerial. 31 represents the usual'input inductance for the rectifier 26, and the usual grid bias batteries 32 are also shown.

It will be apparent from the foregoing 1 that as the loop aerial, which may be tuned to a continuous wave of any frequency, is rotated, the amplitude of the incoming wave is varied to produce an envelope wave which has two maxima and two minima for each revolution of the loop. The a radio frequency currents whose amplitudes are thus varied are amplified by means of the radio frequency amplifier 9 and detected or rectified by the detector 10, thereby deriving 1 if I necessary through; a transformer indi-i i --cated=by thefdotted rectangle 19?-,;to the" other; element of the instrument 1-2.- In Figure 1' the machine 16 is: indicated as a three-phase generator,althouglrthis is;not essential" in fact: the-aerial 1 may: have; .multhwindings and the amplifier and: "recs l I i i tifier devices 9, 10: and :llinay provide mui. ti -phase current for the: instrument 12. a

terminals '23 and 24, and a rotating search i i I l p a a I In Figures 1 and 3 the loops or field coils 2 I f i The wave form of the alternating current thus derived may be corrected to conform to a true sine wave by providing the arrangement between the detector 10 and the lcrnating current and their phaserelation Ill indicated, said phase relation depending uponthe direction of the incoiningradio frequencycurrents.

The position of the peaks of the alternating current waves with respect to any reference plane through the axis of rotation of the loop will depend upon the angle between such plane and the plane of a'great circle cutting the loop center and the transmitter,

- while the position of the peaks of the locally generated alternating current waves with respect to the said reference plane will depend upon the position of the generator field in relation to said reference plane and may be made to coincide therewith. It will thus be apparent that the phase relation between the two waves will determine the dircction of the incoming radio ,frequency wave and may be indicated in terms of direction on the indicator 12.

sion or different transmissions,"the' indicating instruments 12 being, however, adgacent:

to one another, and arranged, for instance on or beneath a map or chart 33, at 34 and 35 respectively, the pointers of such instruments being indicated in 'Figure by arrows 36 and 37 respectively. The points 34 and may represent on a map 38 the position of two receiving stations so that as will be readily appreciated the point 39 at the intersection of the pointers 36 and 37 will represent the position of the ship or aircraft which carries the C. W. transmitter to which the receivers are tuned.

In an alternative arrangement the two rotating aerials may be disposed comparatively close to'one another-or even upon the same shaft and may be turned to receive different transmissions simultaneously. The crossed pointers will then indicate the position of the receiving station and the position of the ship or aircraft may thus be obtained.

WVhen the shaft 5 is driven by synl-chronous motor from any suit-ablefexisting alternating current supply, the" 'latterrmay-- be used as the reference wave instead of the current provided by" the generator 16, and

ratio of the gearing 6 being properlychosen.

As previously herein set forth the one or more phase indicating instruments maybe arranged to provide a record. Such record may be taken continuously or periodically.

It will be understood that various minor modifications may be made without departing fromthe scope of this invention.

1 claim i l. A method of indicating the direction ,of an incoming radio frequency current, which consists in varying the amplitude of said current to produce a Wave having a predetermined frequency, correcting the form of said derived wave to conform to a true sine wave, generating a local alternating current having the same frequency as theproduced wave, and indicating the. phase relation between the. produced wave and the locally generated current.

2. A method of indicating the direction of an incoming radio frequency current, which consists in varying the amplitude of said current to produce a sine wave having a predetermined frequency, generating a local alternatiiig current having the same frequency as the sine wave, adjusting the phase of the local current with respect to a predetermined reference plane, combining said sine wave with the locally generated current, and indicating in terms of direction the phase relation between'the sine wave and the local current.

3. A method of indicating the direction of an incoming radio frequency current, which consists in varying the amplitude ofsaid current at a predetermined frequency to produce an envelope of lower frequency and having approximately the characteristics of a sine wave, rectifying said radio frequency current to derive the sine wave, correcting the form ofsaid derived wave to conform to a true sine wave, generating a local alternating current having the same frequency as the sine. wave, combining the sine wave wlth the locally generatedcurrent, and in-.

dicating the phase relation between said sine wave and-said local "current.

1 LA methodof indicating the direction of an incoming radio frequency current, which consists in varying the amplitude of said current at a predetermined frequency to produce an envelope of lower frequency and having approximately the characteristics of a sine wave, rectifying said radio frequency currents to derive the sine wave, correcting -the form of the derived wave to conform to a true sine wave, generating simultaneously with the variation of the amplitude of the incoming current a local alternating current having the same frequency as the sine wave, adjustingthephase of the local current with respect to a predetermined reference plane, combining the true sine wave with the locally generated current, and indicating in terms of direction the phase relation between said sine wave and said local current.-

5. A method of indicating the direction of an incoming signal wave, which consists in varying the amplitude of. said incoming wave at a predetermined frequency" to produce an envelope wave of a different frequency from that" of the incoming Wave, rectifying the varied amplitude incoming Wave to derive the envelope Wave, correcting the form of the envelope Wave to conform to a true sine wave, generating simultaneously with the variation of the amplitude of the incoming wave a local alternating current having the same .frequency as the envelope wave, combining the envelope wave with the locally generated current, and indicating the phase relation between said envelope wave and said local current.

6. A method of indicating the direction of an incoming signal wave, which consists in varying the amplitude of said incoming wave at a predetermined frequency to produce an envelope wave of a different frequency from that of the incoming Wave, amplifying the varied amplitude incoming wave and then rectifying it to derive the envelope wave, correcting the form of the envelope Wave to conform to a true sine wave, generating simultaneously with the variation of the amplitude of the incoming wave a local alternating current having the same frequency as the sine wave, combining the sine wave with the locally generated current, and indicating in terms of direction the phase relation between said sine wave and said local current.

7. A method of indicating the direction of an incoming signal wave, which consists in varying the amplitude of said incoming wave at a predetermined frequency to produce an envelope wave of a different frequency from the incoming wave, amplifying the varied amplitude incoming wave and then rectifying it to derive the envelope wave, correcting the form of the envelope wave to conform to a true sine wave, amplifying said envelope wave, generating simultaneously with the variation of the amplitude of the incoming wave a local alternating current having the same frequency as the amplified sine wave, adjusting the phase of said local current with respect to a predetermined reference plane, combining the sine wave with the locally generated current, and indicating the phase relation between said sine wave and the said local current.

8. In a radio direction finding system, the combination of a rotatable loop adapted to receive radio frequency currents, means for rotating said loop at a predetermined speed to vary the amplitude of said radio frequency currents thereby producing an envelope wave the frequency of which is determined by the speed of rotation of said loop, means for rectifying said varied-amplitude radio frequency currents to obtain the envelope wave, means for generating a local alternating current of the same frequency as the envelope wave and having a definite phase relation with respect to a predetermined reference plane, said phase relation being varied in accordance with the variation in direction of the incoming radio frequency currents, means for adjustin the phase relation with respect to said re erence plane, and means for indicating said phase relation so that the direction of the incoming radio frequency currents may be determined.

9. In a radio direction finding system, the combination of means for collecting radio frequency currents, means for rotating said collecting means to vary the amplitude of said radio frequency currents, means for deriving an alternating current wave from said radio frequency currents, the frequency of said derived Wave having a definite relation to the speed of rotation of said collect-- ing means, means for generating a local alternating current wave of the same frequency as the derived wave and having a definite phase relation with respect to a predetermined reference plane, said phase relation being varied in accordance with thevariation in direction of the incoming radio frequency currents, means for adjusting the phase relation with respect to said refer ence plane, and means for indicating said phase relation so that the direction of the incoming radio frequency currents may be determined.

10. In a radio direction finding system, the combination of means for varying the amplitude of incoming received radio frequency currents, means for deriving an alternating current wave from said radio frequency currents, the frequency of said derived Wave having a definite relation to the frequency of the amplitude variation of the radio frequency currents, means for correcting the form of said derived wave to conform to a true sine wave, means for generating a local alternating current sine wave of the same frequency as the derived wave, and means for indicating the phase relation between the two Waves.

11. In a radio direction finding system,

the combination 'of means for varying the amplitude of incoming received radio frequency currents, means for deriving an alternating current wave from said radio frequency currents, the frequency of said derived wave having a definite relation to the frequency of the amplitude variation of the radio frequency currents, means for generating a local'alternating current wave of the same frequency as the derived wave, means for adjusting the phase of the locally generated wave, and means for indicating the phase relation between the two waves.

12. In a radio frequency system, the combination of means for varying the amplitude of incoming received radio frequency currents, means for deriving an alternating current wave from said radio frequency currents, the frequency of said derived Wave having a definite relation to the frequency of the amplitude variation of the radio freuency currents, means for correcting the orm of the derived wave to conform to a true sine wave, means for generating a local alternating current sine wave of the same frequency as the derived wave, means for adjusting the phase of the locally generated 19 wave with respect to the derived wave, and

means for indicating thephase relation between the two waves.

In testimony whereof I have signed my name to this specification. ARTHUR WHITTEN BROWN. 

